Electron-tube circuits



March 6, 1928.

J. L. LUDLOW ELECTRON TUBE CIRCUITS Filed Aug:- 31. 1.926 2 Sheets-Sheet INVENTOR. qfaizzj. aakw,

ATTORNEY March 6, 1928. 1,661,698

J. L. LUDLOW ELECTRON TUBE CIRCUITS Filed Aug. 31. 1926 2 Sheets-Sheet 2 7 Tan-'1 INVENTOR.

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BY 6 I 0 AfTORNEY 7 Patented Mar. 6, 1928.

UNITED STATES JOHN L. LUDLOW, for narLnwoon, new JERSEY.

ELECTRON- TUBE CIRCUITS.

Application filed August 31,).926. Serial No. 132,743.

lily invention relates broadly to electron tube circuits and more particularly to. a circuit arrangement for improving the operating efliciency of electron tubes.

One of the objects of my invention is to provide an improved circuit arrangement for the detector tube of a signal receiving system for securing increased efficiency over that heretofore obtainable.

Another object of my invention is to provide an electron tube circuit arrangement for signal receiving systems having extreme sensitivity and high selectivity.

Another object of my invention is to pro vide an electron tube circuit arrangement in which all connection between the negative side of the A or B battery and the grid'is omitted and the input circuit completed by a connection taken to the positive side of the B battery for increasing the operating ability of the tube system.

Still another object of my invention to provide a circuit for an electron tube which will be stable in operation by virtue of the connection of the input circuit across the grid and plate electrodes and the connection of the output circuit across the plate and filament electrodes without a connection between the grid electrode and the negative terminal of the A or B battery.

A still further object ofmy invention is to provide a circuit arrangement for an electron tube wherein the capacity effect of the grid electrode may be concentrated within the tube itself for substantially reducing capacity effects in the circuits exterior of the tube.

My invention will be more fully understood from the specification hereinafter fol lowing by reference to the accompanying drawings wherein:

Figure 1 shows the application of my invention to a radio receiving apparatus employing a detector and three stages of resistance coupled audio frequency amplification; Fig. 2 shows my invention applied to tuning a radio receiver employing a tuned radio frequency amplifier detector and three stages of resistance coupled audio frequency amplification; Fig. 3 shows a modified detector embodying the principles of my invention;

Fig. 4 illustrates my invention as appliedto the detector circuit of a transformer coupled electron tube amplification system; Fig. 5 shows a modified arrangement of detector circuit employed in combination with a re sislancc coupled amplification circuit; Fig. (5 illustrates a further nuuliiication of the circuit arrangement of my invention as ap plied to a detector and resistance coupled amplifier circuit: and Fig. 7 illustrates a detector circuit embodying the principle of my invention and having an additional control element in circuit therewith.

My invention resides in the controlof the operating characteristics of an electron tube circuit for governing the sensitivity, condition of oscillation or regeneration. and sharpness of tuning. Various devices may be arranged in the detector circuit for controlling the factors at the will of the operator and such devices may be conductive, inductive, resistive or capacitii 'e in their nature. The circuit arrangement is such that the grid electrode of the electron tube is absolutely disconnected from the negative side of the 153 battery. The grid electrode is connected to the positive side of the B battery at a point adjacent the plate. The control device may be interposed between the connection from the grid electrode and thepositlve side of the plate for regulating the operating characteristics of the circuit. I The cathode is entirely disconnected from the input circuit The input circuit of or the grid electrode. the electron tube system is therefore positioned across the grid and plate electrodes while the output circuit connects across the plate and filament electrodes. By this circuit arrangement I have found a considerable increase in the sharpness of the tuning of circuits associated with the electron tube and I a large increase in the amplitude of the incoming signaling energy.

Reference character 1 designates an antenna system with which the receiving apparatus is associated cooperating with the ground connection 2, the circuit including the coup ling coil 3 in inductive association. with the secondary inductance 4. The secondary inductance 4 is tuned by means of variable con denser In Fig. 1 the energy from theantenna system is delivered to the input circuit of detector tube 6 having a grid condenser and grid leak 11 in circuit with thegrid electrode 6 of the electron tube with a con ncction from the plate electrode 6 to the input circuit of a resistance coupled audio frequency amplifying system constituted by electron tubes 7, 8 and 9. A common circuit 12 is provided for supplying heating current to all of the cathodes of the several tubes.

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The B battery supply connects to the amplification system at the terminals indicated and the A battery supply is connected to the terminals designated for supplying power to the circuit 12. It will be'observed that there absolutely no electrical connection between the negative side of the cathode, 6" of detector tube 6 and the input circuit 4-5 or the grid electrode (3. The input circuit connect-s through a lead 14 to a point of positive potential 15 adjacent the plate 6 In Fig. 2 I have illustrated my invention as applied to a five tube radio receiving circuit using one stage of radio frequency amplification and plate to grid coupled detector tube embodying the principles of my invention and three stages of resistance coupledaudio frequency amplification. The radio frequency amplification stage has been designated at having the inductance 16 in its input circuit tuned by condenser 17, theinductance 16 being coupled with the primary coupling, coil The output circuit of radio frequency amplifier includes coupling coil 18, which delivers high frequency signaling energy to inductance cl oi? detector tube 6 arranged as described in connect-ion with Fig. 1. There is no electrical connection between the grid electrode (3" and the cathode 6. The detector 6 delivers the rectified energy to the resistance coupled amplification system constituted by tubes 7, 8 and 9. t

In Fi 3 I have illustrated a modified arrangement of circuit for detector tubes where the connection 14 from the input circuit of the tube includes a high resistance 19 .iIlSBl'lGS therewith before terminating at the point in the output circuit of the electron tube system. The interposition of the resistance in the circuit serves to control the operation of the detector circuit preventing a condition of oscillation while maintaining a. condition of extreme sensitivity with the desired degree of regeneration.

In Fig. 4 I have shown the detector circuit. operating in conjunction with the 'adio frequency amplification stage 10 and the transformer coupled audio frequency amplifier constituted by electron tubes 20 and 21, having their circuits coupled with the output of the detector tube and interlinked with each other through transformer 22 and 23.

In Fig. 5 I hive illustrated a modified anangement of detector tube wherein a condenser 24 is arranged in circuit with the lead 1a in series with the input circuit and the output circuit of the electron tube 6. By varying the value of capacity 24 the operation of the detector circuit may be stabilized, the efiect of the incoming signal increased and the circuit rendered extremely selective to the incoming frequency.

In Fig. 6 I have illustrated. a modified circuit arrangement of my invention where connections are established between the grid and plate electrodes of an electron tube amplification system through shunting resis- I have illustrated two stages of amplification constituted by tubes 25 and 226 having their grid and plate electrodes shunted by resistors 27 and 28. The grid electrodes of each of these tubes connects to leads 29 and 30 with resistance 31 to a point 32 adjacent the high potential 15 supply systemr t In Fig. 7 I have illustrated a further system of control for the electron tube detector circuit where the condenser 2-.l in the input circuit of the tube 6 is shunted by means of a variable resistor 33. This arrangement serves to keep the detector grid 6 out of the negative side of the B battery circuit at the same time that the eliiciency ot' the tube system is increased.

I have described certain preferred enibodiments of my invention, but I desire that it be understood that modifications may be made and that no limitations are intended except as may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In an electron tube system the coinbination of an evacuated vessel, grid, filament and plate electrodes in said vessel, input and output circuits intercomiecting said electrodes in non-regenerative relation, :1 source of potential for heating said filament clectrode, a source of potential disposed in circuit with said plate electrode for imparting a positive polarity to said plate electrode, said input circuitbeing substantially independent of said filament electrode with respect to oscillatory currents in said input circuit and having a connection through a resistance with said output circuit to a point adjacent said plate electrode.

2. In an electron tube system an evacuated vessel, grid, filament and plate electrodes within said vessel, :1 source of potential for supplying heating current to said filament electrode, a source of potential for impressing a positive charge upon said plate electrode, an input circuit connected to said grid and plate electrodes, an output circuit disposed between said plate and filament electrodes, said circuits being connected in non-regenerative relation and a composite impedance interposed in the connection between said input and output circuits and connected to a point adjacent said plate electrode. 1

In testimony whereof Iaiiixmy si mature. JOHN ,L. LUD JOIV. 

